When a wellbore is constructed in the earth it is convenient thereafter to deploy electrical logging devices from surface into the well bore to record subterranean data. These logging devices, can be deployed as single devices, like pressure and temperature gauges, or as a long assembly of different devices often referred to in the oil and gas industry as a suite of logging tools attached together in a submersible assembly to the distal end of a submersible electric transmission system commonly referred to as electrical wire line or logging cable.
These logging tools are often deployed in wells in conjunction with explosive submersible perforating guns wherein the logging tools report to surface in real-time via data transmitted up a communication line (typically, an electric wire line), the depth of the perforating logging system in the well thereby enabling the logging operator at surface to trigger devices at a particular required depth by transmitting a signal through the communication line to which they are attached and subsequently fire the subterranean shaped charged guns at the required position in the well.
The vast majority of these subterranean logging tools and perforating systems are electrically powered from surface, a few are powered electrically from subterranean batteries, and still fewer are powered hydraulically. Additionally, it is typical and convenient for the data recorded by the subterranean logging tools to transmit the data in real time from the subterranean environment to the surface via the communication line for recording, and human observation of the data. This data is typically transmitted to surface through electrical communication wires embedded in a wire rope configuration.
The advent of optical fiber construction methods and technology, has resulted in vast increases in data transmission bandwidth. The pioneering of optical power methods from the surface telecommunications industry has presented the potential to transmit vast new amounts of data using light launched through optical wave guides from submersible environments using submersible logging instruments and optical fibers. However, the current logging cables used in the oil and gas industry are not ideally suited to the deployment of optical fiber. This is because the optical fiber, being made out of glass, has different thermal coefficients of expansion and stretch characteristics compared to the wire line logging cable largely constituted from steel wires and tubes. Moreover, when an optical fiber deployed in current logging cable breaks or darkens, the current wire line logging cables are not easily amenable to repair or replacement of the optical fiber. What is needed is a method and cable system that is amenable to both protecting, repairing, and replacing optical fiber in logging cables.
Likewise, in submersible environments offshore in the oil and gas industry, it is often of interest to run submersible electrical transmission lines from the surface to the seafloor. As water depths from which hydrocarbons are extracted continue to get deeper, sometimes over 10,000 feet of water depth, the weight of submersible electrical cables becomes a limiting factor. These systems are often deployed from large coiled reels from barges, and are connected to sub-sea well heads on the distal end of the submersible electrical cable, and return back to the host platforms at the proximal end. The current art teaches towards the use of steel wire and tubes to add strength to these electrical submersible transmission system. The current art also teaches towards the use of bouncy buoys attached to electrical submersible transmission systems, as a means to reduce the weight hanging from surface and said load being transferred to the electrical copper cables. As the oil and gas industry goes into deeper water depths, the density control of the submersible electrical transmission line becomes of interest. What is needed is a means to control the weight and cost of operating and repairing submersible electric transmission cables.
There are fundamental design problems with current industry teaching towards electric wire line logging cable. One such problem is related to the steel wires used as structural members and the combination of these wires and subsequent bundle or wire wrap geometry with the electrical wires and optical fibers disposed in said current well logging cable systems. This class of logging cable is often known as “wire-line” or “electric wire-line” and the method of construction is known to those familiar with the art of wire-rope. Firstly, the initial capital cost of the steel wires used as structural members in the logging wire line of the current state of the art reduces the number of wells that can afford the logging technology. These cables are expensive and difficult to repair. The weight of the additional steel for strength and impact protection of the electrical conductor cable requires expensive surface deployment and retrieval systems sufficient to deploy and extract the heavy electric wire line cables. For example, in ultra-deep wells a dual drum capstan surface logging system must be deployed as the collapse forces and loads on the inner most electrical wire line logging cable wraps on the capstan drum of a simple single capstan system become too great and fail the material of the electrical cable and insulation braided inside the steel wire rope of today's logging systems. This dual drum system is very expensive and its large foot print poses challenges on offshore platforms, rigs, and vessels. Moreover, the inability to repair current electrical wire line logging cables containing multiple braided steel wire rope and steel tube as strength members for the logging cables power and signal transmission members made from copper and silicon dioxide is largely prohibitive. These wire rope (also known as braided wire line) strength members are wound with many layers of wires and then have the electrical transmission members embedded within these wires and in tubes. These arrangements make repair difficult, as splicing and other repair operations involving copious numbers of braided strength wires, tubes and transmission members in a section of electric wire line logging cable becomes difficult, time consuming, and as a result, costly. Hence large amounts of logging line per year are disposed as waste due to the difficulties and costliness of repairing it.
The vast majority of wells are logged with braided electric wire containing multiple opposing layers of braided steel wire. The operators of such cable systems typically remove and discard, from the distal end of the electric wire line logging cable hundreds of feet or more after each operation, which is continually compromised during use. Wire logging line becomes compromised by the auto-gyro affect caused from well logging and the resulting cold working and fatigue stressing induced on the cables. The necessity of the continual removal of the bottom or distal portions of electrical wire line logging cables is due to the mechanical cold working and unwinding of the electric wire of the logging cable as it is run in and out of the well due to the auto-gyro phenomena introduced by well logging. This phenomena is such that the logging tool suite on the distal end of the logging cable are continually experiencing torque as the logging suite continually twists, and auto-gyros while the tools are translated in and out of the well bores. The current manufacturing of electrical logging line involves the use of multiple wraps of opposed direct windings of the braided wire or wire rope to counter act this auto-gyro affect. The current art therefore forces prudent operators to remove and dispose of the lower portion of the logging line continually, to avoid wire line cable failure and the potential loss of logging tools in the wells. Therefore due to the configuration of the currently used logging wire line cables, the cable is inherently damaged in normal operations and there are no quick and inexpensive ways to repair the wire line. It should be noted that while distal portion of current arts logging wire line cable are most often compromised, all portions are subject to fatigue, and wear damage to well gases and liquids having deleterious effects on electrical cable and steel braided wires of the cable.
This auto-gyro twisting phenomena presented by well bores and current logging line systems is a further detriment to the disposal and use of optical fiber within the current wire line configurations for well logging cables. The stretch and twist resistance of optical fibers of the current state of the art logging cables causes severe damage to the optical fibers resulting in large quantities of optical fibers in such logging lines to be broken. Steel wire has vastly different thermal coefficients of thermal expansion and elastic stretch before deformation as opposed to optical fiber, hence current methods of disposing optical fiber in wire lines made of steel is limiting the use of optical fibers. The optical fibers currently used quickly break in the wire rope wire line configurations. Once this occurs the current state of the art does not teach towards repairing or replacement of the logging line nor the optical fiber therein and damaged optical fiber in braided wire line logging cables is discarded as waste. Therefore, the current state of the art offers no commercial means to repair the optical fiber in a broken electrical wire line cable system, nor does it present a logging line system amenable to the differences between optical fiber and steel wire to enhance the life of the optical fibers.
Optical fibers in the current art logging lines fail for many reasons including hydrogen darkening, neutron bombardment, different thermal coefficients of expansion between the optical fiber and the current arts steel wire rope systems, and impacts loads that can shatter the optical fiber like those that occur during perforating.
The invention described herein includes novel combinations of methods of construction, material selection, geometrical dispositions, and repair for the industrial purpose of building a more robust commercial submersible electrical transmission system by incorporating attributes that allow for thermal expansion differences between the electrical conductive members and the optical fiber, ways to replace and repair both the optical fibers in logging line systems, and repair of the logging cable structural members for the enhancement of transmitting electrical, optical, and hydraulic power and signals in my inventions systems. This results in an unexpected low cost commercial improvement over the current art of cutting and disposing of logging line and further has lead to the discovery that the logging cable of the present invention leads to a longer life more durable submersible system, herein referred to as a submersible electrical transmission system.
The present invention includes a coaxial disposition of optical fibers inside tubes of beryllium alloys heretofore not used in submersible transmission lines as electrical conductors. This invention has the industrial purpose of building a more robust and repairable submersible electric transmission system with which to log wells. Moreover, it has been unexpectedly discovered that beryllium alloys impede hydrogen ingression into the optical fibers thereby reducing hydrogen ingress in the coaxial optical fiber disposed in the beryllium alloy tubes of the invention.
A further benefit of the present invention is a geometrical arrangement of the submersible electrical transmission systems constituents such that the beryllium used in the alloys of the present invention reflects a larger portion of neutrons than any current submersible electrical transmission system used for well logging, and thus the invention serves the industrial purpose of shielding the optical system from neutron bombardment triggered by certain submersible logging tools known to those familiar in the art of well logging.
The current state of the art uses highly electrically conductive solid copper wires to reduce the electrical resistance loses. Most submersible environments, sea and ocean, as well as land-based oil and gas wells encounter brine waters where corrosion and chloride stress cracking occurs in many well known materials like copper, stainless steel, and aluminum. Copper, while having a very low electrical resistance is dense and therefore heavy, having a density of approximately 8.94 g/cm3. Copper, has nearly 100% International Annealed Copper Standard (IACS) electrical conductivity, (indeed copper is the basis of the IACS scale for electrical conductivity), has a low material (mechanical) strength comprising a minimum yield strength at 0.2% offset of approximately 70 MPa. Hence copper electrical cable is not sufficiently strong to hang or deploy in a well or in deep offshore cable systems from platforms to the sea floor, as it cannot sustain its own weight to depths much beyond approximately 3,000 feet. Moreover, in well logging operations, it cannot support the weight of hanging a suite of subterranean logging tools, nor tensile or torque loads induced on logging cables in wells, or marine water depths where currents can cause continual movement of submersible cables.